I am having a hard time remembering when they played Enstrom with anyone else. It seems like whenever they were both healthy they generally played together.
Enstrom did tend to have a positive impact on everyone, including Byfuglien.
Enstrom played about 6821 minutes for the Jets 2.0. In that time the team controlled 51.5 percent of shots and 51.0 percent of goals, which is something for a team that was mostly out of the playoffs (which means they were outscored on the whole). The team's share of shots and goals was better with Enstrom on the ice than on the bench by 1.1 and 1.5 percentage points respectively. So from that, we see that Enstrom made the team better.
Of those 6821 minutes, Enstrom has played 2877 minutes with Byfuglien on the ice, although some of that would be when Byfuglien was a forward.
Enstrom's results are indeed better with than without Byfuglien; in part because of chemistry (Byfuglien is all offense and Enstrom is all defense), while part is because Byfuglien was just better than most of the alternatives (anyone not named Trouba).
WAR, specifically the even strength portion, looks at how a player impacts all his linemates and all his opponents.
Fun fact:
Enstrom had the 52nd highest even strength WAR last season in his "bad year" and 35th highest even strength WAR/60...